1. Field of the Invention
The present invention relates to a support structure for an electronic component such as a piezoelectric vibrator, and also relates to an electronic component such as a piezoelectric transformer, a gyroscope and a multilayered piezoelectric component including the inventive support structure.
2. Description of the Related Art
A conventional electronic component and support structure, for example, in the form of a piezoelectric transformer, is shown in FIGS. 17 and 18. A piezoelectric transformer 80 may be used in, for example, a high-voltage power-supply circuit of an inverter for a back light of a liquid-crystal display, an inverter for switching on a fluorescent lamp or a copier, and other similar devices. The piezoelectric transformer 80 includes a piezoelectric transformer element 85 having input electrodes 82 and 83 and an output electrode 84 provided on a piezoelectric plate 81 made of a piezoelectric ceramic in the shape of a rectangular flat-plate. The input electrodes 82 and 83 are arranged so that they are located opposite to each other on the top and bottom surfaces of a half section which in FIGS. 17 and 18 is on the left side of the piezoelectric plate 81 as seen in FIGS. 17 and 18. The output electrode 84 is disposed on the surface on the right side of the piezoelectric plate 81 of FIGS. 17 and 18.
In the piezoelectric transformer 80, the piezoelectric transformer element 85 operates in a fundamental (primary) vibration mode called a xcex/2 mode, wherein a node (node point) N of vibration at which the vibration displacement is zero is present at a position located at one half of a length of the piezoelectric plate 81, and a maximum point of vibration displacement is located at the two ends of the piezoelectric plate 81. Therefore, in such a piezoelectric transformer 80, in order to minimize the suppression of vibration of the piezoelectric plate 81, the piezoelectric transformer element 85 is supported on a mounting substrate 89 at the node N of vibration at which the displacement of the vibration of the piezoelectric plate 81 is minimum.
A conductive bonding agent 86 or the like is used to electrically and physically connect the piezoelectric plate 81 to the mounting substrate 89. Each of the electrodes 82 to 84 is electrically connected by the conductive bonding agent 86 to a terminal electrode 90 disposed on the mounting substrate 89.
As shown in FIG. 17, after the piezoelectric transformer element 85 is placed on the mounting substrate 89 to which the conductive bonding agent 86 is applied in advance, the conductive bonding agent 86 is hardened, and thereby the mounting is completed. Alternatively, the conductive bonding agent 86 is applied to the piezoelectric transformer element 85 in advance and then the transformer 85 including the conductive bonding agent 86 is placed on the mounting substrate 89, the conductive bonding agent 86 is hardened, and thereby the mounting is completed. Alternatively, as shown in FIG. 18, after the piezoelectric transformer element 85 is positioned on the mounting substrate 89, the conductive bonding agent 86 is applied to the side surface of the piezoelectric transformer element 85 by a dispenser 92 and the like, and hardened, thereby the mounting is performed.
In the conventional piezoelectric transformer 80, since the conductive bonding agent 86 used when the piezoelectric transformer element 85 is mounted on the mounting substrate 89 must have a certain degree of elasticity, denatured urethane and silicon, soft epoxy, and the like is used for as a binder material included therein. Although these materials cause the conductive bonding agent 86 to have elasticity, the materials have a weak bonding force. In particular, the bonding force with respect to the solder used in the electrodes 82 to 84 of the mounting substrate 89 is weak, and when an impact or the like is applied to the piezoelectric transformer 80 after it is mounted on the substrate 89, problems such as peeling or removal of the conductive bonding agent 86 from the electrodes 82 to 84 of the mounting substrate 89 occurs.
In order to overcome the problems described above, the preferred embodiments of the present invention provide a novel support structure for an electronic component including a piezoelectric vibrator, a piezoelectric transformer, a gyroscope or a multilayered piezoelectric component, which support structure is constructed to improve bonding strength between a conductive bonding agent and a mounting substrate without decreasing an elasticity of the conductive bonding agent.
The preferred embodiments of the present invention provide a support apparatus for an electronic component including a mounting substrate on which the electronic component is mounted, at least one terminal electrode provided on the mounting substrate, a hole provided on the mounting substrate and located at a position corresponding to a position of the terminal electrode, and a conductive bonding agent disposed in the hole and arranged to electrically connect the electronic component to the terminal electrode.
It is also preferred that the at least one terminal provided on the mounting substrate has a hole formed therein, which hole is located in alignment with the hole formed in the mounting substrate, with the conductive bonding agent being located in the hole formed in the mounting substrate and the hole formed in the at lest one terminal.
The preferred embodiments of the present invention provide an electronic component including a mounting substrate on which the electronic component is mounted, at least one terminal electrode provided on the mounting substrate, a hole provided on the mounting substrate and located at a position corresponding to a position of the terminal electrode, and a conductive bonding agent disposed in the hole and arranged to electrically connect the electronic component to the terminal electrode.
The preferred embodiments of the present invention provide a piezoelectric vibrator including a piezoelectric body and a plurality of input and output electrodes provided on a surface of the piezoelectric body, a mounting substrate on which the piezoelectric body is mounted, a terminal electrode provided on the mounting substrate, a hole provided on the mounting substrate and located at a position corresponding to a position of the terminal electrode, and a conductive bonding agent disposed in the hole and arranged to electrically connect at least one of the input and output electrodes to the terminal electrode.
According to another preferred embodiment of the present invention, a piezoelectric transformer includes a piezoelectric transformer element including a piezoelectric plate and an input electrode and an output electrode disposed on the piezoelectric plate, a mounting substrate on which the piezoelectric transformer element is mounted, a plurality of terminal electrodes provided on the mounting substrate, and a plurality of holes provided in the mounting substrate and located at positions corresponding to locations of the terminal electrodes, and a conductive bonding agent located in the holes and arranged to electrically connect at least one of the input and output electrodes to at least one of the terminal electrodes.
Another preferred embodiment of the present invention provides a gyroscope including a prismatic vibrator with a plurality of piezoelectric elements provided on the surface of the prismatic vibrator, each of the piezoelectric elements including a piezoelectric body and an electrode on the surface of the piezoelectric body, a mounting substrate on which the prismatic vibrator is mounted, a terminal electrode provided on the mounting substrate; a hole provided in the mounting substrate and located at a position corresponding to a location of the terminal electrode, and a conductive bonding agent located in the hole and arranged to electrically connect at least one of the electrodes of the piezoelectric elements to the terminal electrode.
A further preferred embodiment of the present invention further provides a multilayered piezoelectric component including a multilayered piezoelectric element vibrating in a longitudinal vibration mode, the multilayered piezoelectric element having a multilayered body structured in such a way that a plurality of piezoelectric layers and a plurality of electrodes define a plurality of layers which are laminated to each other in an integral stack, the polarization directions of adjacent ones of the piezoelectric layers of the multilayered body being disposed opposite to each other, a plurality of input and output electrodes provided on the surface of the multilayered body, a mounting substrate on which the multilayered piezoelectric element is mounted, a terminal electrode provided on the mounting substrate, a hole provided in the mounting substrate and located at a position corresponding to a location of the terminal electrode and a conductive bonding agent disposed in the hole and arranged to electrically connect at least one of the input and output electrodes to the terminal electrode.
The holes which are provided in the mounting substrate can be through-holes and via-holes which have a conductor provided in an inner wall thereof and also through-holes which do not have a conductor provided in the inner wall, and also blind holes, and other types of holes.
As a result of filling the holes with a conductive bonding agent, the contact area between the conductive bonding agent and the mounting substrate is increased. In addition, with this arrangement of the conductive bonding agent filled in the hole, the conductive agent functions as a wedge so that the conductive agent is firmly and reliably located at the inner wall of the hole. Therefore, the bonding strength between the conductive bonding agent and the mounting substrate is increased.